Amplifier circuits



H. HOLLERITH, JR.. ET AL AMPLIFIER CIRCUITS Filed l lay 14, 1925 July 7, 1931.

alike: map

Patented July 7, 1931 UNITED STATES PATENT OFFICE HERMAN HOLLERITH, J R., F RIVERTON, AND ALMON N. FENTON,

OF AUDUBON, NEW

JERSEY, ASSIGNORS T0 VICTOR TALKING MACHINE COMPANY, A CORPORATION OF NEW JERSEY AMPLIFIER CIRCUITS Application filed May 14,

This invention relates to amplifier circuits,

' and more particularly to amplifier circuits prevent oscillation of an electron discharge amplifer by balancing out the effect of the electrostatic coupling between the plate and grid circuits, internally or externally of the tube, or by greatly reducing the coupling in the radio frequency transformer. If the effect of the electrostatic coupling is neutralized, it has been found necessary to overneutralize at the lower frequencies in order to secure sufficient neutralization to prevent oscillation at the higher frequencies. Thus the sensitivity is greatly reduced at the lower frequencies. If oscillation or regenerative effects are prevented by embodying a loose coupling, amplification is greatly reduced at the lower frequencies. Moreover, methods heretofore employed for controlling the radio frequency amplification, that is for preventing oscillation, have been such that the tone quality of the received signals on distant reception is inferior, due to the trimming of the side bands, etc., as is well understood in the art, and amplification over part of the broadcast frequency range is greatly reduced.

An object of the present invention is to provide an amplifier circuit with novel means for overcoming the above defects.

Another object of the invention is to provide means for preventing cascaded audione from oscillating and at the same time secure a maximum of amplification over a wave length band.

Broadly stated, the invention consists in providing coupled circuits, one or more of which are resonant to the frequencies to be received, but which are so arranged that the voltages and currents in a succeeding stage will be neither in phase nor 180 out of 1925. Serial No. 30,281.

phase with that in the preceding, but will be at some intermediate phase relation whereby it is possible to produce a greater amplification per stage before the point of oscillation is reached, and this without effecting the broadness of tuning whereby equal amplifications of the side bands along with the carrier wave is secured with greatly improved quality of reproduction.

Two forms of the inventive idea are shown in the accompanying drawings, which drawings, however, are for the purpose of illustration only and are not to be taken as a. definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings,

Fig. 1 shows diagrammatically two thermionic amplifiers connected in cascade in accordance with the present invention;

Fig. 2 is a diagrammatic view illustrating a second manner in which audions may be operatively associated in accordance with the present invention; and

Figs. 3 and 4 are vector diagrams illustrating the results that are secured by the circuit arrangement of the present invention.

Referring to the drawings, wherein like reference characters refer to like parts throughout the. several views, and particularly to Fig. 1, the present invention is shown embodied in a circuitwhich includes the input terminals 1 and 2, of an electron discharge device 3, that are connected in any desired manner to a suitable current source (not shown). Across the output-terminals 2 and 4 of the audion discharge device 3 are connected, in the usual manner, the primary 5 of a radio frequency transformer 6, and the usual battery 7 for supplying the necessary voltage to the output terminal or plate 4. Inductively associated with the primary winding 5 is the secondary winding 8 of the radio frequency transform er, which secondary winding is preferably tuned to the desired frequency in a well known manner by means of a variable condenser 9 in shunt thereto. The coupling between windings 5 and 8 may be closer than that usually employed in the well known coupled to one portion of the secondary than to the remainder of the same.

In order. to employ a close coupling between" the windings of the transformer 6 and at the same time to avoid objectionable sociated with the secondary winding 8 which constitute a loadcontrollable in phase, and

amountv whereby it is possible to maintain a coupling between the windingswhich, at frequencies in the broadcast range will give large amplification without regenerative dis-v tortion. In the form shown, this means is constitutedby a condenser 10 in series with a resistance llg said condenserand resistance beingshunted across a part of the secondary.

windingS, as indicated at the points 12 and 7 13 on the latter. If desired, the connection 7 13 may be made atwa suitable point 14 on a lead 15 connectin glthe secondary winding 8 and the tuning condenser '9," or the connection 13 may be made at a suitable point'l6 in the tuned circuit 9,- .8,15 as indicated in'dotted lines. The input terminalsll' and 18fof 'a second electron discharge device or vacuum tube 19, may be connected in the usual manner to the secondary winding 8 and tuning condenser 9, or the same may be connected to any other desired circuit are rangement; I I

' Operation-4f a signal voltage is applied to the input terminals 1 and2 of the electron discharge device 3 b'y means of some suit ablepick-up,- such as a tuned loop or an antenna and ground, and any common type 7 tuner (not, shown); saiduvoltage is enlarged and reproduced, beween the output terminals 2 and 4 in a manner well understood in the overithe range. used. In other words,: as. .the dynamic characteristic of the electron art. This enlarged voltage or output will differ from the input voltage in a manner which depends on the dilference between the load in the output'circuit and a pure 'resis tance, and upon the nonlinear character-,.

istic of the plate current-grid voltage curve 7 discharge device-deviates from a straight line -to a loop form, distortion is present. The

fio-wl of the alternating current through the primary Winding 5 'of the transformer 6 induces a voltage in the secondary winding 8 which. latter is tuned to resonance with a 1 desired signal by means of the condenser 9.

' By shunting apart of the secondary winding 8 with? the capacity'lO and resistance 11,

a load which is controllable in phase and amount is transferred by the close coupling 1 .to the electron discharge device=3r 'By cor-r .rec'tly apportioning the the secondary which are shunted, the capacity and the resistance, it is possible to maintain number of turns of a couplinggldetweenthe windings of the transformer 6,, which at all frequencies in the broadcast-range will give a maximum ampl-ification without regenerative distortion: or

oscillation. This will be clear fronrEigu-res'i electron discharge device 3, regenerative efi'ects, or oscillat on of the electron di'scharge device 3, means are 'as'-" B is the externalresistance drop, 'i X is the external reactance drop, 7

0 z' Z =the-A. Cavolt'age on the plate 4, e g is the voltageiinduced inthe secondary winding of the transformer; 6-:When the pri-- mary andsecondary v'ofsaidctransformer are woundin the SQIDB'CllIGClZlOII,

fl is the voltage inducedln, the secondary winding of the transformerfi when the wind ings of the latter are wound in opposite directions, V

CB is the component of the plate voltage in phase with the grid voltage, and p "A is the component of the plate voltage which must be in phase with the grid voltage before the tube 8 will oscillate; 7

From-an inspection of Fig. 3 it will be seen that as the load introduced by the capacity 10 and the resistance 11 isincreased, the

voltage e g induced in the secondary winding 8 is of such a phase that the platevoltage 6D is not materially affected by the capacity effect, resulting from the close coupling be- 7 tweenthe primary and secondary windings of thetransformer 6. Thevector represent ing'the-plate volt age isparallel to thevector r V r L z lfi representing the external impedance. As the latter is decreased or as the external resistance drop z' R is'de'creased (see Fig. l),i

proves'the exactness of reproduction, ortends to eliminate distortion. Moreover, increase of the load introduced by'capa'city lOandresistance 1'1 materially increases the breadth of the peakof the resonance curve without affecting the broadness of-j tuning. This results in equalamplification'ofthe-entire side bands, al.ong 'w-1th the 'carrierwave, thereby greatly improving the-quality of reproduction. Y

In Fig. ,2 there is illustrated another form of the present invention wherein the primary of a transformer 21 is formed in two parallelly connected sections 20*and'20 and the battery/7 is connected to said' primary winding intermediate the sections, asata point 22, and the outer endsof the-two sections of the primary winding} are;connectedftogether at a point 23 in the lead to the plate 4 of the electron discharge device 3. The secondary winding of the transformer 21 is also formed in two parallelly connected sections 2 1 and 24 and the filament 18 of a second electron discharge device 19 is connected to the secondary winding intermediate the sections 24* and 24 as by means of a. suitable conductor 25. In shunt with a suitable number of turns of each of the sections 24 and 24, which are in close coupling with the sections of the primary Winding, is a conductor 26 which is connected in series with a condenser 10 and a re 'sistance 11, which latter is connected at a suitable point 27 to the conductor 25. A tuning condenser 9 is preferably in parallel with the sections of the secondary winding, and the opposite ends of the latter are connected at a point 28 to the conductor 29 leading to the grid 17 of the electron discharge device 19.

It will be understood that the number of turns of the secondary to be shunted by the capacity and resistance, the value of the capacity, and of the resistance will vary in accordance with the elements of the circuit, as for example,the internal resistance of the audion or audions employed, etc. However, one example will be given which is capable of producing superior results in an ordinary receiving apparatus:

From the primary winding in two sections, 53 turns in each section, of #36 D. S. C. wire; form the secondary winding in two sections, 80 turns in each section of #36 D. S. C. wire. Connect 40 turns of the secondary, 20 in each of the sections, in series with a .003 mfd. capacity and a 400 ohm resistance. The thickness of the insulation between the primary and secondary coils may be 3/32 of an inch and said coils may be wound in the same direction.

The two sections of each of the primary and secondary are wound on the same axis and in the same sense, but the secondary may be wound in eitherthe same or the opposite sense from the primary. In the form shown in Fig. 2 the battery 7 is connected to the point of junction of the two sections of the primary, the two ends of said sections be ng connected in the circuit to the plate 4; similarly the filament of the tube 19 is shown as connected to the point of junction to the two sections of the secondary, the two ends of said sections being joined in the lead to the grid 17 It: is to be expressly understood, however, that it is within the contemplation of this invention to reverse either or both of these connections, i. e., the lead from the plate 4 may be connected to the point of j unction of the two sect-ions of the primary, with the two ends of said sections connected to the battery; and the lead to the grid 17 may be connected with the point of unction of the two sections of the secondary, with the ends of said sections connected to the filament 18. While the shunted capacity and resistance have been shown as applied only in the secondary circuit, advantageous results can be obtained by applying the shunted capacity and resistance in the primary circuit either with or without shunted capacity and resistance in the secondary and whether the primary and secondary are formed in one or more sections. It is also to be expressly understood that where the primary and secondary are formed in sections, said sections may not be equal, the number of turns in the two sections of the primary may be different or the turns in the two sections of the secondary may be different or the number of the turns in both the primary and the secondary may be different. lVhile the closely coupled sections of the primary and secondary have been shown as adjacent the point of junction of the sections of the primary and secondary, the closely coupled sections could equally well be adjacent the opposite ends of the sections of the secondary, or the section of the secondary which is not closely coupled with the primary can be more or less removed from the closely coupled section of the secondary, or placed in non-inductive relation therewith and suitably connected in series with the closely coupled section. While as above pointed out it is preferred to wind the two sections of the primary and the two sections of the secondary in the same sense, either or both of the primary and secondary could have their sections wound in the opposite sense by connecting the corresponding ends of the reversely wound sections. The extent to which the sections of the primary and the sections of the secondary may be separated from each other may also be varied.

It is therefore to be expressly understood that the specific arrangement illustrated on the drawings and the specific example of a construction of a transformer above given are only by way of illustration and not to be taken as in any way defining the limits or uses of this invention.

The present invention is particularly adapted for use in combination with the radio frequency amplifier tubes used in receiving sets. The device may be used in combination with any desired number of such tubes, with any suitable detecting means and audio-amplifying means. Reference will therefore be had to the appended claims for a definition of the limits of the invention.

lVhat is claimed is:

1. In combination with a plurality of vacuum tubescomprising grid, filament and plate electrodes, means including closely coupled primary and secondary windings for connecting said tubes in cascade, and means in shunt to a portion only of said secondary winding for preventing oscillation of one or more of said -tubes'dueto the coupling between said windings. I

' 2. In av'acuuni tube amplifier system comprising two' or-more tubes in cascade, couplingnie'ans for said tubes including primary winding, a secondary winding, a portion of said" secondary being'closely coupled .to the primary, mean-sfor tuning said secondary winding, and means for maintaining the cur.-

rent-induced in the closely coupled portion of the secondary at a phase different from the inducing voltage, the total inductive and-capacitative reactan'ce 'of the secondary'winding being maintained at resonance value through the range of broadcasting fre quencies; i 3LIn-an amplifier system the combination of a vacuum tube having an output circuit, a second circuit, and means for coupling-said 20" output and second-circuits, said means comprising primary and secondary windings, and

means in shunt to a portion'only of said secondary winding for maintaining the voltage induced therein at a differentphase from that of the inducing current.

4. In an amplifier system the combination of a vacuum tube having an output circuit, a second circuit, and" means for coupling said output a-nd'second circuits,'said means comprising primary and secondary windings,

and means for controlling the feed back to saidvacuum tube including a capacity and a resistance in series, said last named means 7 being in shunt to EtPOItlOIl only of said secondary.

5. '-In an amplifier system, the combination of an audion having an out-put circuit, a second circuit, and means for, inductively cou-' pling said; circuits including primary and secondary windings,and means including ca .pacityfandin shunt w th a portion only oi said secondary for securing'large amplification=over the broadcastrange and for pre- [venting oscillation of said audion.

' GJRa'dioreceiving apparatus comprising a plurality ofelectron discharge devices, a

V transformer operatively connected to two of j of said transformer, and a cap'acity'and resistance in series one with the other and in" said devices, meansfor'tuning'the secondary shunt with a portion only of the windings of said secondary;

" tron discharge device having an output circuit, an inputfcircuit, a transformer connect-- 7. An amplifier system comprising an elecing said circuits, one portion of the secondary ofthe transformer being closely coupled to v the primary thereof, and means in shunt with means including an input circuit, a trans theclosely coupled portion of said secondary for controlling the feed-back to said device.

'8. A circuit of the class described compr sing an amplifier having an output circuit,

former connecting said input and output circuits; a plurality of series mpedances in shunt with a portion only ofthe secondary of said transformer, and means 'foriresonating the transformer to a desiredfsignal fre-' quency;

9.- A' device for operatively connecting radio frequency amplifier tubes comprising a primarywindin'g, a secondary winding-inductively associated with" said primary wind- 7 ing, one portion 'of the secondary winding being closely coupled'wi'tli th'e'primary-wind ing,.and impedances insliunt to said closely coupled portion only for changing thephase of the voltage induced in said second-ary.

winding.- I p I r v I 10. An amplifier system coin-prising ian electron discharge "device having output electrodes, a sectional winding connected to said electrodes, a secondary winding inductively associated with said first named wind-- ing, said secondary being formed in'sections, means for completing an electrical circuit connected to said secondary winding, and a series capacity andresistance'in shunt to a portion of each of thesections of saidsecond ary winding.

11. Radio receiving apparatus comprising a plurality'of electron discharge devices, a

transformer operatively connected to two of said devices, means'for tuning the secondary electrical circuit connected to said secondary winding, and means in shunt to a portion only of said secondary for preventing oscillation of said device. 7 g

13; An amplifier "circuit I comprising an electron discharge devicehaving output electrode's, alprimary winding connected to said electrodes, means including'a secondary Winding inductively and closely associated with a portion only of said primary winding, and means in shunt to said secondary winding for maintaining the current induced in the secondary at a 'dilferent phase from that of the inducing voltage. a

14.- An amplifier system comprising an electron discharge device having output electrodes, asectional winding connected to said electrodes, a secondary winding inductively associated with said first named winding, said secondary being formed in 'sections,"means for completing an electrical circuit connected to said secondary winding, and series impedances in shunt with a portion of said'se'condary windin p i i 15 An amplifier systemcomprising an electron discharge device having anroutput circuit, an input circuit, a transformer con-1 ids necting said circuits, one portion of the secondary of the transformer being closely coupled to the primary thereof, and a capacity and a resistance in shunt with the closely coupled portion only of said secondary for controlling the feed-back to said electron discharge device.

16. An amplifier system comprising an electron discharge device having output electrodes, a primary winding connected to said electrodes, a secondary winding inductively associated with said primary, and means in shunt to a portion only of one of said windings for preventing oscillation of said discharge device.

17. An amplifier system comprising an electron discharge device having output electrodes, a primary winding connected to said electrodes, said windinghaving sections connected in parallel, a secondary winding formed in sections inductively associated with said primary winding, and loading means in shunt with a portion only of one of said windings.

18. An amplifier system comprising an electron discharge device having output electrodes, a primary winding connected to said electrodes, a secondary winding inductively associated with said primary, one of said windings being formed in sections with the sections connected in parallel, and loading means in shunt to a selected portion only of one of said windings.

19. An amplifier system comprising an electron discharge device having output e1ec= trodes, a primary winding having parallelly connected sections, the center of said winding being connected to one of said electrodes and the ends of said winding being connected to the other of saidelectrodes, a sectional sec ondary winding associated with said primary winding, the sections of the secondary being parallelly connected, and loading means connected to said secondary winding.

20. In an amplifier system, the combination of a thermionic tube having an aperiodic output circuit, a second thermionic tube having a tuned input circuit a portion of which is inductively coupled to said output circuit, and means for detuning the coupled portion ofv the input circuit whereby the voltage across said portion is out of phase with the current traversing the same.

21. In an amplifier system, the combination of a thermionic tube having an aperiodic output circuit, a second thermionic tube having a tuned input circuit a portion of which is inductively coupled to said output circuit, and means for putting the consequent capacitative coupling of said circuits into an interphase relation with the inductive coupling.

In testimony whereof we have signed this specification.

HERMAN HOLLERITH, J R. ALMON N. F ENTON. 

